Problem: Simplify the following expression: $k = \dfrac{5g}{20g + 20h} - \dfrac{30h}{20g + 20h}$ You can assume $f,g,h \neq 0$.
Answer: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{5g - (30h)}{20g + 20h}$ $k = \dfrac{5g - 30h}{20g + 20h}$ The numerator and denominator have a common factor of $5$, so we can simplify $k = \dfrac{g - 6h}{4g + 4h}$